From: Jiri Pirko <jiri@resnulli.us>
To: "Michael S. Tsirkin" <mst@redhat.com>
Cc: Pankaj Gupta <pagupta@redhat.com>,
linux-kernel@vger.kernel.org, netdev@vger.kernel.org,
davem@davemloft.net, jasowang@redhat.com, dgibson@redhat.com,
vfalico@gmail.com, edumazet@google.com, vyasevic@redhat.com,
hkchu@google.com, wuzhy@linux.vnet.ibm.com, xemul@parallels.com,
therbert@google.com, bhutchings@solarflare.com, xii@google.com,
stephen@networkplumber.org
Subject: Re: [RFC 2/4] tuntap: Publish tuntap maximum number of queues as module_param
Date: Wed, 20 Aug 2014 13:53:44 +0200 [thread overview]
Message-ID: <20140820115344.GD1916@nanopsycho.orion> (raw)
In-Reply-To: <20140820114907.GA17943@redhat.com>
Wed, Aug 20, 2014 at 01:49:07PM CEST, mst@redhat.com wrote:
>On Wed, Aug 20, 2014 at 01:46:20PM +0200, Jiri Pirko wrote:
>> Wed, Aug 20, 2014 at 01:17:24PM CEST, mst@redhat.com wrote:
>> >On Wed, Aug 20, 2014 at 12:58:17PM +0200, Jiri Pirko wrote:
>> >> Mon, Aug 18, 2014 at 03:37:18PM CEST, pagupta@redhat.com wrote:
>> >> > This patch publishes maximum number of tun/tap queues allocated as a
>> >> > read_only module parameter which a user space application like libvirt
>> >> > can make use of to limit maximum number of queues. Value of read_only
>> >> > module parameter can be writable only at module load time. If no value is set
>> >> > at module load time a default value 256 is used which is equal to maximum number
>> >> > of vCPUS allowed by KVM.
>> >> >
>> >> > Administrator can specify maximum number of queues only at the driver
>> >> > module load time.
>> >> >
>> >> >Signed-off-by: Pankaj Gupta <pagupta@redhat.com>
>> >> >---
>> >> > drivers/net/tun.c | 13 +++++++++++--
>> >> > 1 files changed, 11 insertions(+), 2 deletions(-)
>> >> >
>> >> >diff --git a/drivers/net/tun.c b/drivers/net/tun.c
>> >> >index acaaf67..1f518e2 100644
>> >> >--- a/drivers/net/tun.c
>> >> >+++ b/drivers/net/tun.c
>> >> >@@ -119,6 +119,9 @@ struct tap_filter {
>> >> >
>> >> > #define TUN_FLOW_EXPIRE (3 * HZ)
>> >> >
>> >> >+static int max_tap_queues = MAX_TAP_QUEUES;
>> >> >+module_param(max_tap_queues, int, S_IRUGO);
>> >>
>> >> Please do not introduce new module paramaters. Please other ways to
>> >> interchange values with userspace.
>> >
>> >I suggested this initially, but thinking more about it, I agree.
>> >
>> >It's a global limit (necessary to limit memory utilization by
>> >userspace), but it should be possible to change it
>> >after module load.
>> >
>> >Additionally, userspace that has the FD should be able to
>> >retrieve the value without guessing that the FD is
>> >for the tun device (and not e.g. macvtap).
>> >To retrieve the value, an ioctl is probably the
>> >cleanest approach.
>> >
>> >To set it, how about a sysctl? I think the limit can also apply to
>> >all devices, not just tun.
>>
>> Or netlink?
>
>Are there examples of netlink being used to set global defaults
>as opposed to per-device parameters?
That is so far not possible. But I believe that it can be implemented.
I'm just thinking out loud.
>
>> >
>> >--
>> >MST
next prev parent reply other threads:[~2014-08-20 11:53 UTC|newest]
Thread overview: 19+ messages / expand[flat|nested] mbox.gz Atom feed top
2014-08-18 13:37 [RFC 0/4] Increase the limit of tuntap queues Pankaj Gupta
2014-08-18 13:37 ` [RFC 1/4] net: allow large number of rx queues Pankaj Gupta
2014-08-18 17:43 ` Sergei Shtylyov
2014-08-19 5:15 ` Pankaj Gupta
2014-08-18 13:37 ` [RFC 2/4] tuntap: Publish tuntap maximum number of queues as module_param Pankaj Gupta
2014-08-20 10:58 ` Jiri Pirko
2014-08-20 11:17 ` Michael S. Tsirkin
2014-08-20 11:46 ` Jiri Pirko
2014-08-20 11:49 ` Michael S. Tsirkin
2014-08-20 11:53 ` Jiri Pirko [this message]
2014-08-21 4:30 ` Jason Wang
2014-08-22 11:52 ` Pankaj Gupta
2014-08-24 11:14 ` Michael S. Tsirkin
2014-08-25 2:57 ` Jason Wang
2014-08-26 15:30 ` Pankaj Gupta
2014-08-18 13:37 ` [RFC 3/4] tuntap: reduce the size of tun_struct by using flex array Pankaj Gupta
2014-08-25 1:35 ` David Gibson
2014-08-18 13:37 ` [RFC 4/4] tuntap: Increase the number of queues in tun Pankaj Gupta
2014-08-25 1:37 ` David Gibson
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